1. Go to https://search.
2. Type in a search term for the background you seek (ex. Ocean)
3. Uncheck the box for "commercial use" and leave the box checked for "modify, adapt, build upon"
4. On the right, toggle advanced settings and uncheck the box next to "Photos," while leaving "Videos" checked.
5. IMPORTANT: On the left, next to "Safe Search On," toggle the left-most arrow to select one of the following:
- Modifications Allowed
- No Known Copyright Restrictions or
- US Government Works
6. View footage with the play arrows.
7. Click on a video to select it. Scroll down to view and jot down the attribution information (or use the ImageCodr or Flickr CC Attribution tools to generate an attribution that you can add to your video).
8, When you find footage with the Creative Commons license you want, select the download symbol (a downward pointing arrow) on the right and save the video to your PC.
9. Convert the file to a .mov (I'm not sure why the .mp4 format was not working in the DoInk app on my iPad, since it is a supported format, but it wasn't).
10. Upload the .mov file to Google Drive or DropBox. From there, you can open the video directly from the DoInk Green Screen app by selecting the "video" option (the icon of a filmstrip), "locations," and either Google Drive or Drop Box.